Preliminary evaluation of Italian everbearing strawberry cultivars using a qualitative integrated approach

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Preliminary evaluation of day-neutral strawberry cultivars

cultivated in Italy using a qualitative integrated approach

Nicole Roberta Giuggioli

1

_{, Rosanela Briano}

1

_{, Priscila Alvariza}

2

_,

Cristiana Peano

1

_{Department of Agricultural, Forest and Food Sciences, University of Torino, Torino, Italy}

2

_{Departmento de Fitotecnica, Faculdade de Agronomia Eliseu Maciel, Universidade Federal}

de Pelotas, F Pelotas, Brasil

*Corresponding author: nicole.giuggioli@unito.it Abstract

Giuggioli N.R., Briano R., Alvariza P., Peano C. (2018): Preliminary evaluation of day-neutral strawberry cultivars cultivated in Italy using a qualitative integrated approach. Hort. Sci. (Prague), 45: 29–36.

In this study the texture profile, total soluble solids (TSS) and the fruit skin colour of four day-neutral strawberry cul-tivars cultivated in Italy (‘Anabelle’, ‘Murano*’, ‘Portola*’ and ‘Triumph’) was evaluated at four harvest times. The inter-relationships of the analysed parameters were determined using principal component analysis in order to suggest the best commercial scenario (local market, supermarket retailer or export) for each cultivar. Data analysis related to texture and TSS contents revealed that ‘Anabelle’, ‘Portola*’ and ‘Murano*’ displayed unique characteristics, and that ‘Triumph’ showed lower values for these parameters. Due to its low hardness and cohesiveness values ‘Anabelle’ could be suited to a short supply chain; ‘Portola*’, meanwhile, might meet the requirements of a long supply chain, due to its high hardness and low TSS (P £ 0.05); ‘Murano*’ could be distinguished from the other cultivars by its high luminosity (ranging from 41.46–46.21 L*); while ‘Triumph’, due to its darkness (36.83–37.13 L*), could be suitable for a local/farmers’ market.

Keywords: colour; Fragaria × ananassa; market; quality index; texture

The strawberry (Fragaria × ananassa Duch) crop is characterised, more than any other berry, by the number of different systems used for its pro-duction (tunnel, greenhouse, open field, soilless) and the numerous breeding programs used for this species (Capocasa et al. 2008; Martinelli, Michelangelo 2012). The major market chan-nels for strawberries, as for the majority of fresh produce, are the regional and national wholesale markets and direct/local channels. Of the Euro-pean countries, Italy is the fourth largest straw-berry producer, producing approximately 140,000 t on a surface of 3,700 ha (Neri 2012; Turci 2013; Franceschini 2015). ‘Portola*’ is the major culti-var grown in Northern Italy, accounting for 60% of total strawberry production. Colour, pulp firmness, taste, flavour and nutritional value are considered the main quality parameters for consumer

accep-tance of fresh fruits (Kubota et al. 2012; Orne-las-Paz et al. 2013; Rios De Souza et al. 2014). Ares et al. (2009) developed an objective sensory quality index for strawberries, based on consumer perception; however, it was not suited to quality control in strawberries or their shelf life prediction, revealing the difficulty in evaluating product qual-ity using a single index. Although strawberries have been classified as a non-climacteric fruit (Kader 1991), physicochemical changes continue to oc-cur during storage. Strawberry cultivars with high pulp hardness could suit a supply chain with the longest transport time, due to their extended shelf life and resistance to mechanical damage; however, the influence of this property on texture and fla-vour perception at the time of consumption needs to be considered. The texture of strawberries has been widely reported (Caner et al. 2008; Kartal

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et al. 2012; Aday, Caner 2013). However, texture was not correlated with the subjective assessment of freshness, which was more dependent on lumi-nosity (Arce-Lopera et al. 2012). The freshness perception of strawberries involves the various at-tributes of appearance, odour, texture in hand and mouth, and flavour (Peneaú et al. 2007).

In this work strawberries were evaluated for sev-eral quality parameters (mechanical properties, to-tal soluble solids (TSS) and colour) of importance to consumer acceptance. Four day-neutral straw-berry cultivars (‘Anabelle’, ‘Murano*’, ‘Portola*’, and ‘Triumph’) grown in Northern Italy were inves-tigated and the most appropriate market channel for each was suggested. The cultivars ‘Anabelle’, ‘Murano*’,‘Portola*’ and ‘Triumph’ are present on the Italian varietal list (Faedi et al. 2014) and their characteristics are listed in Table 1.

MATERIAL AND METHODS

Plant material. Four day-neutral strawberry

cultivars (‘Anabelle’, ‘Murano*’, ‘Portola*’ and ‘Tri-umph’) were grown in the greenhouse of Agrifrutta srl, a private company located at the foot of the mountains in Peveragno (Cuneo), Northwest Italy. All plants were grown in the same soilless tunnel.

Ninety fully red strawberries were harvested ear-ly in the morning, on a weekear-ly basis from August 5 to August 23 in the year 2014 (Table 2), and once harvested, all cultivars were immediately trans-ported at 4°C to the laboratory for qualitative anal-ysis. To evaluate the texture profile analysis (TPA) characteristics and skin colour three replicates consisting of 30 individual fruits (90 fruits in total) were sampled for each cultivar and for each harvest time. The same fruits were mashed, homogenised and used for determination of TSS content and ti-tratable acidity. Three replicates were measured for this last analysis. To best evaluate the interrelation-ships among analysed data within strawberry culti-vars a principle component analysis (PCA) analysis was performed.

Texture profile analysis. Texture profile

analy-sis (TPA) of the freshly harvested strawberries was performed using a TA.XTplus texture analy-ser (Stable Micro Systems Ltd., UK), with a 30 kg

Table 1. Harvest time for strawberries and relative dates

Harvest time Date

I August 5, 2014

II August 11, 2014

III August 17, 2014

IV August 23, 2014

Table 2. Fruit characteristics for all day-neutral varieties

Cultivar and origin Patent Owner Fruit description References

‘Anabelle’ (France) – Interna-Angier

tional

The dimension of the fruits is medium/small with a conical/oblongata shape. The external colour is red and

the brightness is low. The colour of the pulp is orange/ red with a low firmness. The fruit is sweet in taste and has low acidity. The aroma and organoleptic quality are

medium/high.

Faedi 2014; Baroni et

al. 2015

‘Portola*’ (USA) (EU) 28654 2008/1505

(EU)

Davis, California University

The dimension of the fruits is big with a conical shape. The external colour is bright red and the brightness is

elevated. The firmness of the fruits is high.

Shaw, Larson 2009 ‘Murano*’ (Italy) 13694935 (US) 2012/1731 (EU) CIV, Consorzio Italiano Vivaisti

The dimension of the fruits is medium/big with a coni-cal shape. The external colour is red and the brightness is high. The colour of the pulp is light red with a high firm-ness. The sweet taste and acidity are medium. The aroma

and organoleptic quality are medium.

Faedi 2014; Baroni et al. 2015 ‘Triumph’ (USA) _20140157465US P1 Plant Sci-ence, Inc.

The dimension of the fruits is medium with a conical shape. The external colour of the berries is red (rang-ing from red to dark red), the glossiness range is from medium to strong. The firmness of the fruits is medium,

the quality is good and the fruit aroma is good.

Ackerman et al. 2014 *cultivars that have the patent

Vol. 45, 2018 (1): 29–36 Hort. Sci. (Prague)

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load cell. Compression tests were performed on whole fresh fruits maintained at room temperature (18°C ± 1°C) with the following parameters: a 75-mm aluminium compression plate (P/75), 5 75-mm/s pre-test speed, 1 mm/s test speed, 8 mm/s post-test speed, penetration distance 4 mm and rest pe-riod of 5 s between cycles, trigger force 1.0 N and 5 N trigger force. Values of hardness, adhesiveness, cohesiveness, springiness, gumminess, chewiness and resilience were automatically calculated from the resulting force-time curve using Texture Expert Version 1.17 software (Caner et al. 2008). The defi-nitions of each textural parameter are reported in Table 3. The average of 90 fruits for each cultivar and harvesting time were calculated.

Total soluble solids and fruit skin colour. The TSS

of juice extracted from each strawberry was measured using an Atago Pal-1 pocket refractometer (Atago Co. Ltd., Japan), and expressed as °Brix at 20°C.

The skin colour of each fruit was measured us-ing a tristimulus reflectance colorimeter (Minolta

Chroma Meter, Model CR-200b, Japan) equipped with an 8-mm diameter measuring area. Colour was recorded using the CIEL*_a*_b*_{uniform colour} space, where L* _{indicates lightness, a}* _indicates chromaticity on a green (−) to red (+) axis, and b* chromaticity on a blue (−) to yellow (+) axis. The average TSS and surface colour of 90 fruits for each cultivar and harvesting time were calculated.

Statistical analysis. All statistical analyses were

performed using SPSS Statistics 22 software pack-age (2013, IBM, Italy) for Mac. The obtained data were analysed using a two-way analysis of variance (ANOVA), and the means were separated using Tukey’s test (P ≤ 0.05). When the interactions were significant, the mean values were compared using a least significant difference (LSD) multiple range test, at P ≤ 0.05 significance. To correlate the com-bined parameters of TPA, TSS and colour, the data were standardised and a PCA was performed. A va-rimix rotation was used to restrict the components to those that had high factor loadings.

Table 3. Description of the TPA, sensory parameters and calculations

TPA Parameters Description Sensory Calculation

Hardness (N) Maximum force required to _{compress the sample} Force required to compress a substance between molar

teeth

The peak force of the first com-pression cycle Cohesiveness

(dimensionless) be deformed before it rupturesExtent to which a material can

Degree to which a substance is compressed between the

teeth before it breaks

Measured as the area of work during the second compression divided by the area of work during

the first compression Springiness

(elasticity) (dimensionless)

How well a product physi-cally springs back after it has been deformed during the first compression. The spring-back is

measured at the downstroke of the second compression.

Degree to which a product returns to its original shape

Distance of the detected height of the product on the second

com-pression

Chewiness (N) a solid food to steady state for Energy required to masticate

swallowing

Length of time required to masticate the sample, at a constant rate of force

applica-tion, to reduce it to a consis-tency suitable for swallowing

Gumminess × springiness

Gumminess (N)

Energy required to disintegrate a semi-solid material to a state ready for swallowing: a product of a low degree of hardness and a high degree of cohesiveness

Denseness that persists throughout mastication: energy required to disinte-grate a semi-solid material to a state suitable for swallowing

Hardness × cohesiveness

Resilience

(dimensionless) How well a product ‘fights’ to regain its original position –

The area during the withdrawal of the first compression, divided by the area of the first compression references: Yang et al. 2006; Singh et al. 2013; Nishinari et al. 2013

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RESULTS AND DISCUSSION Texture profile analysis

The TPA of strawberries has been previously used to examine differences in the quality of strawberry cultivars (Rasing et al. 2003; Caner et al. 2008). In the present study, multivariate linear analysis of the acquired TPA data was used to identify differ-ences among four strawberry cultivars (‘Anabelle’, ‘Murano*’, ‘Portola*’ and ‘Triumph’), as a function of harvest time (Table 4). All the considered TPA parameters, with the exception of adhesiveness and springiness, were influenced by cultivar and harvest time, and their interaction. Hardness, adhesiveness and cohesiveness are the main textural attributes associated with the sensory and rheological prop-erties of organic matrices (Nishinari et al. 2013). Hence, Fig. 1 limits the TPA to these three textural attributes, which are further discussed herein.

Hardness is the max. force required to compress the sample and was calculated from the peak force of the first compression cycle (Fig. 1a). The four strawberry cultivars showed significant differences (P £ 0.05) in hardness at each harvest time. Hard-ness values on August 5 (first harvesting time) were 8,118.2 ± 1.75, 7,337.4 ± 1.30, 5,021.1 ± 1.45 and 4,517.2 N ± 1.59 for ‘Portola*’, ‘Murano*’, ‘Triumph’ and ‘Anabelle’, respectively. ‘Portola*’ was the firm-est throughout the entire harvfirm-est period, followed in decreasing order by ‘Murano*’ > ‘Triumph’ > ‘Anabelle’. Relative hardness for each cultivar was higher on the final two harvest dates compared to the first two (differences of +3.68%, +22.67%, +22.42% and +34.55% for ‘Anabelle’, ‘Portola*’, ‘Mu-rano*’and ‘Triumph’, respectively, between the first

and the last harvest). This trend is probably due to the 5°C drop in temperature at the end of the sec-ond harvest time (data not shown) and confirms the positive relationship between the temperature of the fruit and its firmness in the strawberry (Rose et al. 1934).

Adhesiveness represents the tendency to be sticky and describes the mucilaginous nature of the strawberry. No significant differences in adhesive-ness were observed among the cultivars, irrespec-tive of the harvest date. However, the lowest adhe-siveness values were recorded on August 17 and 23 (last two harvest dates; Fig. 1b). Adhesiveness is an important factor in post-harvest handling of straw-berries, hence August 17 and 23 were key harvest dates. Fruits that undergo long transport periods require low adhesiveness values at harvest, as this parameter can increase with storage (Caner et al. 2008). Solubilisation of pectin material in the mid-dle lamellae (Caner et al. 2008) of the fruit cor-responds to decreased cohesiveness. Furthermore, cohesiveness plays an important role in mouthfeel towards the end of mastication by the molar teeth (Bourne 2002). ‘Anabelle’ had significantly lower cohesiveness than the other cultivars throughout the harvesting period. On the second and fourth harvest, ‘Portola*’, ‘Murano*’ and ‘Triumph’ had similar cohesiveness (P > 0.05).

Total soluble solids

The TSS is mainly influenced by the total sugars and organic acids, which, in turn, are influenced by the cultivar and stage of ripeness. All four cul-tivars had significantly different TSS values at each

Table 4. Multivariate linear analysis for texture profile analysis, total soluble solids (TSS), (°Brix) and colour param-eters (L*, a* and b*) of strawberry cv. ‘Anabelle’, ‘Portola*’, ‘Murano*’ and ‘Triumph’

H ar dne ss A dhe sive -ne ss Spr ing ine ss Cohe sive -ne ss Gummine ss C he w ine ss Re silienc e TS S L * a * b* Cultivar 0.01 0.80 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Harvesting time 0.01 0.12 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.84 0.00 Cultivar*harvesting time 0.01 0.63 0.32 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

when interactions were significant, the mean values were compared using a least significant difference (LSD) multiple

range test with P < 0.05 considered significant; L* _{– lightness; a}* _{– chromaticity on a green (−) to red (+) axis; b}*_–

chro-maticity on a blue (−) to yellow (+) axis

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harvest time (Table 3, Fig. 2; P ≤ 0.05). ‘Anabelle’ had the highest TSS, ranging from 7.79–9.06°Brix. In contrast, ‘Portola*’ had the lowest TSS, ranging from 5.64–5.77°Brix. Soft strawberries are per-ceived to have high sweetness even though they may have soluble sugar contents similar to those of harder fruits (Kohyama et al. 2013). The TSS values of all four cultivars, with the exception of ‘Portola*’, increased significantly as a function of harvest time (data not shown). Differences in straw-berry TSS across harvest dates have been associ-ated with changes in plant physiological state and environmental conditions. According to Hasing et al. (2013), cultivars that maintain a stable TSS

throughout the fruiting season would be highly de-sirable, due to their uniform eating quality. For this reason, ‘Portola*’ would be the preferred cultivar to maintain eating quality at the end of the season when the overall market supply increases, but also when environmental conditions cause adverse ef-fects associated with high TSS in the fruit.

Fruit skin colour

Anthocyanins, carotenoids and chlorophylls are the main pigments responsible for the colour of strawberries (Nunes et al. 2006). Bright, red

straw-

0 2,000 4,000 6,000 8,000 10,000 12,000 I II III IV Har dnes s (N)

Anabelle Portola* Murano* Triumph

-70 -60 -50 -40 -30 -20 -10 0 I II III IV A dh es iv en es s ( g) n.s. n.s. n.s. n.s. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 I II III IV C oh es iv en es s( –)

0.00 2,000.00 4,000.00 6,000.00 8,000.00 10,000.00 12,000.00 I II III IV Har dnes s (N)

–70 –60 –50 –40 –30 –20 –10 0 I II III IV A dh es iv en es s ( g) n.s. n.s. n.s. n.s. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 I II III IV C oh es iv en es s( –)

0.00 2,000.00 4,000.00 6,000.00 8,000.00 I II III IV Har dnes s (N) -70 -60 -50 -40 -30 -20 -10 0 I II III IV A dh es iv en es s ( g) n.s. n.s. n.s. n.s. 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 I II III IV C oh es iv en es s( –)

Fig. 1. Texture profile analysis (TPA): (a) hardness, (b) adhesiveness, and (c) cohesiveness for the ‘Anabelle, ‘Portola*’_,

‘Murano*’_{and ‘Triumph’ during the 4 harvesting times}

the means regarding the harvest time, followed by different letters are significantly different at P ≤ 0.05 according to Tukey’s test

(a)

(b)

(c)

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0 2 4 6 8 10 12 I II III IV °B rix

b a b d a a a b a _b a c a c a a

Fig. 2. Total soluble solids (TSS) (°Brix) for the 4 strawberry cultivars during the 4 harvesting times

means regarding the harvest time, followed by different letters are significantly different at P ≤ 0.05 according to Tukey’s test

0 5 10 15 20 25 30 35 40 45 50 I II III IV Ligh tn es s L*

a b a b a c a c b d a c b c a a 0 5 10 15 20 25 30 35 40 45 I II III IV C hro m ati ci ty a* a d c b a d b c a d b c a d a b 0 5 10 15 20 25 30 35 40 45 50 I II III IV C hr omaticit y b* a c a b a a b a c d a c b c a b 0 5 10 15 20 25 30 35 40 45 50 I II III IV Ligh tn es s L*

a b b c a c a b a d a c b c a a 0 5 10 15 20 25 30 35 40 45 I II III IV C hro m ati ci ty a* a d c b a d b c a d b c a d a b 0 5 10 15 20 25 30 35 40 45 50 I II III IV C hr omaticit y b* a c a b a a b a c d a c b c a b

Fig. 3. Fruit external colour parameters: (a) lightness (L*), (b) chromaticity on a green (−) to red (+) axis (a*_{), and (c)}

chromaticity on a blue (−) to yellow (+) axis (b*_{; (c)) for the 4 strawberry cultivars during the 4 harvesting times}

the means regarding the harvest time, followed by different letters are significantly different at P ≤ 0.05 according to Tukey’s test

TSS (°Br

ix)

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berries are more suited to supermarkets compared to dark strawberries, due to high consumer accep-tance. Table 3 shows that L*_{was strongly infl uenced} by the cultivar and harvest time, and their interaction. Th e highest L*_{values were obtained for ‘Murano*’ and} ranged from 41.46–46.21 (L*_{), while ‘Triumph’ had the} lowest with a L*_{range of 36.83−37.13 (Fig. 3).} Statisti-cally signifi cant L*_{diff erences among all the cultivars} were observed from the start of the second harvest time until the fi nal harvest (August 23), at which stage the following L*_{values were obtained: ‘Anabelle’ 42.10} ± 2.92 (L*_{); ‘Portola*’ 40.60 ± 3.66 (L}*_{); ‘Murano*’ 46.21} ± 3.96 (L*_{) and ‘Triumph’ 37.13 ± 3.22 (L}*_).

Principal component analysis

PCA is a useful tool to identify patterns in data and highlight their similarities and diff erences (Rodriguez-Delgado et al. 2002; Šamec et al. 2016). PCA has been used successfully to evalu-ate the interrelationships among certain physical and chemical attributes within strawberry cultivars (Šamec et al. 2016). Th e PCA used in the present study showed that 74.87% of the variability was ex-plained by the fi rst three components: PC1, PC2 and PC3 accounted for 41.67%, 21.90% and 12.78%, respectively, of the variability (Fig. 4). Th e fruit skin colour parameters (L*_{, a}*_{and b}*_{values) and TSS} contents were markedly diff erentiated from the texture parameters. Indeed, they were grouped in PC2, which can be described as the colourfulness-quality group. Most of the TPA parameters (hard-ness, gummi(hard-ness, chewi(hard-ness, cohesiveness and resilience) were grouped together in PC1, while springiness and adhesiveness were combined in

PC3. Th is was probably because springiness and adhesiveness are primarily correlated with the vis-cosity properties of an organic matrix.

CONCLUSION

On the basis of this preliminary study of day-neutral cultivars cultivated in Northern Italy, it can be concluded that ‘Anabelle’, ‘Portola*’, ‘Murano*’ and ‘Triumph’ had distinct attributes when meas-ured against a single qualitative standard. How-ever, evaluation of their qualities against multiple indices was not possible. Th e cultivars were dis-tinguished based on their texture, colour and TSS, and, therefore, these parameters are a potentially useful means of identifying their most appropri-ate market channels. ‘Anabelle’, ‘Portola*’ and ‘Mu-rano*’ exhibited unique texture characteristics and TSS contents; ‘Triumph’ showed lower values for these characteristics. ‘Anabelle’ could be ideal for a short supply chain, such as a farmers’ market, as it displayed the lowest hardness and cohesive-ness, suggesting that it may be susceptible to the deformation stresses that occur during transport and shipping. Its high TSS content can be consid-ered more suitable and may be appreciated by con-sumers particularly interested in traditional taste. ‘Portola*’exhibited the highest hardness and low-est degree of change in TSS throughout the harvlow-est period, suggesting that it may have a relatively long shelf life and suit the longest supply chain. ‘Mura-no*’was diff erentiated from the other cultivars by its high L*_{. Th is cultivar showed intermediate} tex-ture characteristics, and, therefore, could be suited to either a short or long supply chain. Due to its dark colour, ‘Triumph’ may suit a local/farmers’ market. All four cultivars should be further evalu-ated with respect to nutraceutical attributes and fl avour, as well as post-harvest properties.

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Received for publication May 26, 2016 Accepted after corrections January 2017